Whole new mooring (mushroom , chain, ball) in 2001. Left it in 3 years,
figuring less rusting than sitting in a yard over the winter and better
holding as the mushroom buried itself. . Checked upper links with diving
periodically and all was well.

After haling out the boat 3 weeks ago , I noticed the top shackle was
sliding into the ball,(junk) and I called the yard to have it pulled. Yard
guy was out of town, said he'd get to it this week. I check on it
yesterday, and the ball and 10 feet of chain have drifted off to shore.

The chain ends with a shackle and a swivel ; the bottom of the swivel is
fine. This means (?) that the top link of the heavier chain has rusted, and
that it must have gone from being able to hold a 30 foot sailboat to powder
unable to hold itself in 3 weeks.

Is this possible ?